Human beings have a biological rhythm, which corresponds to the brightness and the darkness during the day and night, that is, a circadian rhythm in which sleeping and awakening are repeated at an almost daily cycle. A hormone called melatonin is related to this rhythm. Melatonin has an action of decreasing the body temperature and promoting sleep, but secretion of the hormone is suppressed by being exposed to strong light at night. That is, it is suggested that light exposure at night disturbs the circadian rhythm, and therefore, there is a possibility that the light exposure causes poor health such as sleep disorders. For this reason, a countermeasure method is required which is effective, widely used, and inexpensive.
Patent Document 1 discloses a device and spectacles including an optical filter. Patent Document 1 discloses a method of maintaining a circadian rhythm using the disclosed device and spectacles.
Patent Document 2 discloses an optical filter which selectively absorbs light of a specific wavelength, and light shielding spectacles using the optical filter.
Patent Document 3 discloses a light source system and an illumination device using a plurality of luminescent materials. It is also disclosed that, according to Patent Document 3, it is possible to obtain an effect by adjusting the intensity of the luminescent materials while maintaining the brightness and the color of the luminescent materials. Patent Document 4 discloses a display filter containing a specific porphyrin compound. Patent Document 5 discloses a spectacle lens containing a specific porphyrin compound.